5 Use of biological resources Flashcards
What can be used to increase the yield of certain crops?
Glasshouses
Polythene Tunnels
Allow control over limiting factors of photosynthesis
Increasing the yield of crops: Glasshouses or Polythene tunnels
- Paraffin Heater (optimum temp. for enzymes, produces CO2 as it burns)
- Artificial lighting (plants don’t have to stop photosynthesus at night)
- Prevents entry of pests
How does fertiliser increase the crop yield?
When plants don’t have enough minerals, their growth + life processes are effected.
Sometimes the soil has ran out of the mineral as it has been used by a differnt crop
So fertilisers provide minerals.
Reasons for pest control
Pests feed on crops, damaging them, reducing their yield
Advantages of Pest Control
Less plants damaged by pests -> increases crop yield
Disadvantages of Pest Control
Chemical, poisonous to humans so must use very little to avoid harming other wildlife
Biological Control
Alternative to pesticides
Using other organisms to reduce pests
Advantages of Biological Control
Longer - lasting effect
Less harmful to wildlife
Disadvantages of Biological Control
Can become a major pest themselves
Role of yeast in the production of food including bread
- Bread dough contains flour, water and sugar and yeast
- When left to rise, enzymes break down the carbs into sugar, and this sugar is used in aerobic respiration (produces CO2)
- When the oxygen runs out, anaerobic respiration occurs instead. Produces CO2 (air pockets) an ethanol = fermentation.
- These air pockets expand -> bread rises.
- When put in the oven, fermentation continues until enzymes are denatured. Ethanol evaporates away.
5.6 practical: investigate the role of anaerobic respiration by yeast in different conditions
- Mix together sugar, yeast and distilled water in text tube
- Add layer oil to make sure anaerobic respiration occurs
- Seal with bung and attach with delivery tube connecting to test tube of water.
- Put 1st test tube in water bath and count bubbles produced.
- No. of bubbles/time taken = rate of CO2 production = rate of anaerobic respiration
- Repeat experiment with different temperature water baths
Can be improved by using a gas syringe instead of water tube.
Fermentation
When microorganisms break down starch to produce energy
Production of yogurt
- Sterilise equipment to remove unwanted microbes + chemical contamination
- Milk is pasteurised at 85 -95 degrees for 12-30 minutes
- It is then homogenised
- Milk is cooled then Lactobacillus is added
- Mixture of milk + lactobacillus is incubated
- Thickened yogurt is stirred and cooled
Why is milk pasteurised?
To kill unwanted bacteria to avoid competition for lactose with lactobacillus
Why is milk homogenised?
To disperse fat
The longer it is homogenised for, the lower fat yogurt
Why is milk cooled before Lactobacillus is added?
So that enzymes do not denature
Why is the milk incubated?
Lactobacillus digests milk proteins + ferments the lactose sugars to form lactic acid
Increases acidity/lowers pH to prevent growth of other harmful microbes + thickens milk to yogurt
Fermentors
To grow microorganisms in large quantities
Parts of Fermentor
- Input for microbial culture
- Paddle Stirrer
- Gas outlet
- Probes (pH and temperature)
- Stainless steel vessel walls
- Water jacket
- Air inlet
Process of Natural Selection
- There is variation within the organisms of a species
- Changing conditions in the environment favour a characteristic over others
- Those better adapted to the environment survive and reproduce + become more common in the population
- Those less adapted to the environment die
What is natural selection
Life started at simple organisms from which all large complex organisms evolved
